Recently, the amount of file data which companies handle tends to increase, and the cloud storage technique draws attention in view of unitary management of the file, scalability and continuity of business affairs and the like. In the cloud storage technique, for example, there is a type of technique in which file storage is disposed in a client site, and the file data of the file storage is archived to be stored in object storage of a remote site. In this case, there is a demand of the client that the old file archived in the object storage is necessary to be restored by the operation performed in the client side. In order to meet this demand, it is necessary to maintain a correspondence between file identifiers of the file storage disposed in the client site and file identifiers disposed in the object storage of the archive destination.
Herein, as methods for backing up the file from file storage to separate file storage, PTL 1 and PTL 2 are known.
In the PTL 1, a method is disclosed in which a plurality of files is collectively compressed to back up the compressed file. In the case of the backup, the correspondence between a path which is an identifier in the backup source of the backup target file and a snapshot ID which is an identifier in the backup destination is managed in the backup destination.
In the PTL 2, a method is disclosed in which the file is backed up in a remote object storage from local file storage. In the file storage described in the PTL 2, the file is identified with a path or an inode number. Further, a correspondence between the path and the inode number is managed by the file storage. In the backup method described in the PTL 2, a backup source manages the correspondence between an inode number of a backup source file and a URL which is an identifier of the backup destination object.